The formation of the neuromuscular synapse requires muscle-specific receptor kinase (MuSK) to orchestrate postsynaptic differentiation, including the clustering of receptors for the neurotransmitter acetylcholine. Upon innervation, neural agrin activates MuSK to establish the postsynaptic apparatus, although agrin-independent formation of neuromuscular synapses can also occur experimentally in the absence of neurotransmission. Dok-7, a MuSK-interacting cytoplasmic protein, is essential for MuSK activation in cultured myotubes; in particular, the Dok-7 phosphotyrosine-binding domain and its target in MuSK are indispensable. Mice lacking Dok-7 formed neither acetylcholine receptor clusters nor neuromuscular synapses. Thus, Dok-7 is essential for neuromuscular synaptogenesis through its interaction with MuSK.

Seedling establishment on fallen logs is a major regeneration system for tree species in boreal forests. Seedling survival on fallen logs is affected not only by the microsite environment but also by the genetic factors of individuals. To quantify the genetic effects on seedling longevity, we identified seedlings using a number tag system and collected needles of Picea jezoensis and Abies sachalinensis established on fallen logs in spring 2006. Survival or death of each seedling was investigated during 2006-2012. We genotyped seedlings with microsatellite markers and calculated individual-based multilocus heterozygosity (MLH) for each seedling. A Cox proportional hazards model was applied to evaluate the effects of MLH on seedling longevity of the two species considering the fallen log conditions. The model indicated that MLH positively affected seedling longevity in P. jezoensis, whereas the effects of MLH were not significant in A. sachalinensis. Here, we discuss differences in the effects of MLH on seedling longevity between the two species, considering species characteristics and MLH frequency distribution. Keywords